Depression of noncarbonaceous material during flotation



Patented nFan. 21, 1941 stares DEPRESSION F NONCARBONACEOUS MATERIALDURING FLOTATION Robert B. Booth, Springdale, Comp, assignor to AmericanCyanamid Company, New York, N. Y.,

a corporation of Maine No Drawing. Application March 7, 1939, Serial No.260,342

8 illairns.

This invention relates to froth flotation, and more particularly toimprovement in the flotation of noncarbonaceous ores having finelydivided gangue.

Many ores have finely divided gangue or a portion of the gangue in afinely divided or slimy condition which frequently creates difficultiesby reason of contamination of the concentrate by the fine gangue or bythe action of the fine 10 gangue on the mineral values, preventing theirready flotation and thus reducing recoveries. In many cases, bothfactors are involved.

In the past, starch and other organic protective colloids have commonlybeen used for the depression of gangue during flotation. However, thesefrequently cause the depression of certain of the desired constituentsof the ore as well as the gangue and hence decrease recoveries.

According to the present invention, I have found that froth flotation ofnoncarbonaceous ores is improved when it is carried out in the presenceof dextrines which efliciently depress gangue without excessivedepression ofmetal values when used in amounts suficient to giveefiective gangue depression. This result is surprising because while theprior art teaches the use of organic protective colloids as flotationagents, the dextrines of the present invention are very poor protectivecolloids. In fact, they can hardly be called protective colloids at all,and yet they are better gangue modifiers than most good protectivecolloids.

The term dextrine is frequently loosely applied in the industry to covera large number of degraded cellulosic products. According to the presentinvention, however, dextrine is used in its strict sense as covering theproducts obtained by substantially dry heat degradation of cellulosicmaterial such as starch with or without preliminary treatment withmaterial such as acids. The term dextrine will be used in no other sensein the present application and is not intended to include materialsobtained by digesting starch in various aqueous solutions which aresometimes loosely referred to as dextrinized products. These latterproducts do not exhibit the properties of true dextrines in theflotation of ores and are not included in the scope of my invention.

While all true dextrines show the valuable properties set out above,difierent dextrines will vary in the degree to which they possess theseproperties and in general, the best results are obtained with yellowcorn dextrines which result from the dry heating of corn starches whichhave been pre-treated with acids such as nitric acid.

. The amounts of dextrine required will vary to some extent with the oreand with the dextrine. In all cases, it is necessary to use sunficientamounts of dextrine to eflectively depress 5 the gangue, but the amountshould not be large enough to seriously depress metal values. To someextent, this may be considered as a compromise but it is an advantage ofthe present invention that an amount of dextrine, random 10 larly ofyellow corn dextrine, which gives very effective gangue depression iswell below the amount that seriously depresses metal values,particularly in pyritic ores. In general, efiective depression ofnoncarbonaceous gangue beit gins with amounts of dextrine from about 0.2lb./ton' to 0.3 lb./ton, depending on the dextrine.

In the case of some ores, amounts of dextrine as high as 6 lbs/tonhave'been used with success. In general, however, it is desirable to {2keep the dextrine as low as possible and with most ores amounts ofdextrine from 1 to 2 lbs/ton give good results but, of course, theinvention is not limited to this particular range. In some cases, theore to be floated is of low 25 grade and a compromise may be desirablein the amount of dextrine used since the larger amounts of reagentrequired would cost more and not be worth it.

The present invention may be used in rougher 30 flotation of the orewhere desired or it may be used only in a cleaning operation. Theadvantage of the invention is particularly high in cleaning andtherefore the best operating procedure may involve a rougher floatwithout dex- 35 trine or with smaller amounts of dextrine.

It is an advantage of the present invention that it is not limited toany particular flotation procedure. For example, the addition of thedepressing agents of the present invention need 40 not take place priorto flotation. The point at which they are introduced, whether'in thegrinding circuit, classifier, etc., will depend on the particular orebeing floated.

The exact mechanism by which the dextrines of the present inventionoperate has not been definitely determined and the present invention isnot limited to any theory of action. It is probable that two factors maybe involved, one an alteration of the surface of the gangue so 50 thatit does not attach itself to the bubbles during froth flotation. Thismight be called a true depressing action. The second factor may lie inthe dispersing of fine gangue particles and therefore preventing themfrom adhering to minthe eral values which are to be floated. It is alsopossible that these factors may be effective in varying degrees in thecases of different ores and no limitation to any particular theory ofaction is intended in the present invention, the above discussion beingmade for the purpose of advancing what appears to be the most probablereason in the light of present knowledge. It is possible that otherfactors may also be effective.

I have described and claimed the use of dextrines in the depression ofcarbonaceous gangue in my Patent No. 2,145,206 dated January 24, 1939,and the present case is not intended to include the depression ofcarbonaceous material. The invention will be described in detail in thefollowing specific examples in conjunction with various dextrines andwith difierent typical noncarbonaceous ores. The invention is, ofcourse,

conditioned with the following reagents: secondary butyl xanthate, 0.15lb./ton; a fifty-fifty mixture of sodium diethyland disecondarybutyl-dithiophosphates, 0.05 lb./ton; and pine oil, 0.062 lb./ton.Flotation was effected in Fagergren flotation machines and in Test #4the pulp was conditioned with 2.0 lbs/ton yellow corn dextrine; in Test#5 with 3.0 lbs/ton yellow tapioca. dextrine; in Test #6 with 3.01bs./t0n white corn dextrine; in Test #7 with 3.0 lbs/ton white potatodextrine. The results of these tests were compared with those of Test#3, similarly conducted except that no dextrine was employed and withthose of Tests #8 and #9 in which were used 2.0 lbs/ton soda ash (Test#8) and 2.0 lbs. sodium silicate per ton (Test #9), two reagentsfrequently used to overcome slime interference during flotation.

Feed Concentrate Tailing Test No.

GS Oz./ton Wt., Ratio z./ton Rec. per- Wt., 0z./ton Rec. per- .Aupercent cone. Au cent Au percent Au cent Au not limited to the detailsof the specific examples Example 3 which are typical illustrations only.

Example 1 A gold ore from South Africa containing pyrite, chalcopyrite,bornite, pyrrhotite, quartz and sericite and assaying 0.396 to 0.410oz./to-n Au and about 92.5% insoluble, was subjected to flotation withand without yellow corn dextrine. The ore was conditioned with thefollowing reagents: secondary butyl xanthate, 0.35 lb./ton; a fiftyfiftymixture of sodium diethyland disecondary butyl-dithiophosphates, 0.03lb./ton; and pine oil, 0.062 lb./ton. Flotation was effected in Fager-Comparative flotation tests with and without yellow corn dextrine wereconducted on a copper ore containing a large amount of talcose materialand assaying 1.05-1.12% copper and about 64-65% insoluble. The followingreagents were used: secondary butyl xanthate, 0.075 lb./ton, and pineoil, 0.031 lb./ton. Flotation was effected in Fagergren flotationmachines. In Test #10 no depressant was used; in Test #11 yellow corndextrine, 0.5 lb./ton, was agitated with the pulp prior to the additionof the above-listed reagents.

Feed Concentrate Teilings' 'Iest Gs Cu, Wt., Ratio Cu, 2 Bee. per- Rec.Total, Wt., Cu, Rec. Cu,

percent percent conc. percent cent On insol. percent percent percentpercent 10..... 601. 4 1. l2 14. 53 6. 88: 1 5. 45 70. 54 12. 20 85. 470. 39 29. 46 ll 600.5 1.05 10.94 9.14:1 7.00 73.33 8.32 89.06 0.31 26.67

gren flotation machines and prior to the treat- Example 4 ment with theabove-listed reagents, the pulp was conditioned in Test #2 with 0.5lo./ton yellow corn dextrine. The results of Test #2 were compared withthose of Test #1, similarly conducted except that no dextrine wasemployed. The results ofthese tests are as follows:

Comparative flotation tests with and without yellow corn dextrine wereconducted on a magnetite ore from Pennsylvania containing about 0.8%copper as sulfldes. The gangue was composed mainly of talc, sericite,mica, and quartz Feed Concentrate Telling GS Oz./ton Wt., Ratio Oz./tonRec. per- Rec. per- Wt., 0z./ton Rec. per

' Au percent cone. Au cent Au cent ins. percent Au cent Au Example 2 andthe characteristics of the ore were such that A gold ore from thePhilippine Islands, containing gold, pyrite, chalcopyrite, azurite,quartz, magnetite, and limonite and assaying 0.308 to 0.326 oz./ton Au,was subjected to flotation with and without dextrine. This ore exhibiteda slime interference during flotation. The ore pulp was during theconcentration of the copper by flotation a rather voluminous froth wasproduced. This froth has a tendency to carry a substantial amount ofgangue and fine magnetite and thus the grade of the concentrate incopper is lowered. In addition to improving the metallurgy, 1

the use of yellow corn dextrine aided materially in overcoming thisexcessive frothing. The following reagents were used: sodium isopropylxan-thate, 0.20 lb./ton, and a synthetic alcoholhydrocarbon frother,0.06 lb./ton. Flotation was effected in Fagergren flotation machines andin Test #12 yellow corn dextrine, 0.5 lb./ton, was agitated with thepulp prior to adding the above listed reagents. In Test #13, no dextrinewas ence of a dextrine in amounts sufficient to eliminate a majorportion of the slimy gangue from the concentrate, the flotation takingplace in the presence of a promoter for the values of the ore.

3. A method of floating noncarbonaceous base metal ores containingbarren, non-metalliferous, slimy gangue which comprises subjecting anaqueous pulp of the noncarbonaceous base metal ore to froth flotation inthe presence of a dextrine in used. amounts sumcient to eliminate amajor portion Feed Concentrate Tailings T tN es G pe ut pz c i'it E pe ce nt g pzyc e iit pe c zant g l:::::::::::::::. 329:2 8:??? $133 E1322$323 33% 3515. 8:522 tit The aboveexamples demonstrate that dextrines ofthe slimy gangue from the concentrate, the floof the present inventionmay be used effectively for the depression of noncarbonaceous gangueduring flotation. In the case of the above-described gold ores, anincrease in the ratio of concentration, an increase in the gold contentof the concentrate, and a decrease in the recovery of insoluble in theconcentrate resulted at the expense of only a relatively small loss ingold recovery. Thus, for example, referring to the results of Example 1,the addition of yellow corn dextrine to the ore pulp increased the ratioof concentration about 30% and the gold content of the concentrate about70%, while the gold recovery decrease was less than 2%.

In the case of the copper ores, no compromise is necessary. The additionof yellow corn dextrine, for example, to the ore pulp of Example 4increases the ratio of concentration about 20%, the copper content ofthe concentrate about 25% and the copper recovery about 2%.

The above examples illustrate the application of my invention to typicalmetallic ores, but it is equally useful with non-metallic ores such as,for example, the flotation of cement rock and the like.

It is an advantage of the present invention that since the grade ofconcentrate and ratio of concentration in all cases is increased by theaddition of a dextrine as a gangue depressant,- shipping and treatmentcharges on such concentrates are less in cases where the concentratesmust be shipped for further treatment and this fact makes the process amore economical one than those of the prior art.

What I claim is: i

1. A method of floating noncarbonaceous metallic ores containing barren,non-metalliferous, slimy gange which comprises subjecting an aqueouspulp of the noncarbonaceous ore to froth flotation in the presence ofdextrine in amounts suiflcient to eliminate a major portion of the slimygangue from the concentrate, the flotation taking place in the presenceof a promoter for the values of the ore.

2. A method of floating noncarbonaceous precious metal ores containingbarren, nonmetalliferous, slimy gangue which comprises subjecting anaqueous pulp of the noncarbonaceous precious metal ore to frothflotation in the prestation taking place in thepresence of a promoterfor the values of the ore.

4. A method of floating noncarbonaceous'metallic ores containing barren,non-metalliferous, slimy gangue which comprises subjecting an aqueouspulp of the noncarbonaceous ore to froth flotation in the presence ofyellow corn dextrine in amounts sufficient to eliminate a major portionof the slimy gangue from the concentrate, the flotation taking place inthe presence of a promoter for the values of the ore.

'5. A method of floating noncarbonaceous precious metal ores containingbarren, nonmetalliferous, slimy gangue which comprises subjecti'ng anaqueous pulp of the noncarbonaceous precious metal ore to frothflotation in the presence of yellow corn dextrine in amounts sufficientto eliminate a major portion of the slimy gangue from the concentrate,the flotation taking place in the presence of a promoter for the valuesof the ore.

6. A method of floating noncarbonaceous base metal ores containingbarren, non-metalliferous, slimy ganguewhich comprises subjecting anaqueous pulp of the noncarbonaceous base metal ore to froth flotation inthe presence of yellow corn dextrine in amounts sufficient to eliminatea major portion of the slimy gangue from the concentrate, the flotationtaking place in the presence of a promoter for the values of the ore.

7. A method of floating a noncarbonaceous gold ore containing barren,non-metalliferous, slimy gangue whichcomprises subjecting an aqueouspulp of the gold ore to froth flotation in the presence of yellow corndextrinein amounts sufficient to eliminate a major portion of the slimygangue from the concentrate, the flotation taking place in the presenceof a promoter for the values of the ore.

' 8. A method of floating a noncarbonaceous copper ore containingbarren, non-metalliferous, slimy gangue which comprises subjecting anaqueous pulp of the copper ore to froth flotation in the presence ofyellow corn dextrine in amounts sufficient to eliminate a major portionof the slimy gangue from the concentrate, the flotation taking place inthe presence of a promoter for the values of the ore.

ROBERT B. BOOTH.

